On Wed, Jul 28, 2004 at 10:23:15AM -0400, Rick Stoneking wrote:
> Has anyone done the modifications listed on the FT-736 2m Power amplifier
> schematic that changes the output to 10W? We are converting a 736 to be a
> UHF station (222, 432, 902, 1296) and are using a transverter for 902 to
> 2m. The transverter has a 10W input max, so we would like to permanently
> set the 2m output to 10W so that we do not have to worry about adjusting
> output power when changing bands. Hoping to get confirmation that the
> changes listed on the schematic work okay.
At N5XU, we have an FT-726R that we use with an amplifier (AM-6155) with a
10W max power input requirement, so we faced basically the same problem
as you. For us, the best solution was to add an attenuator in the
transmit-only side of the T/R relay on the amplifier. This was relatively
easy because the amplifier's T/R relay was an external Dowkey coaxial
transfer relay. Our attenuator is a length of some fairly lossy coax
like RG-58 that we computed to have enough dB of signal loss at 144 MHz
to bring the transmit signal down to 10W. We just roll it up with a
cable tie - it doesn't take up much space, it handles 20W of input power
no problem, and because it's on the transmit-only side of the relays,
it doesn't affect receive signal strength at all. There's no way the
rig can overdrive the amplifier.
Depending on how your transverter T/R switching is done, this might work
for you as well.
--
Kenneth E. Harker WM5R
kenharker@kenharker.com
http://www.kenharker.com/
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